Acoustical plaster



COATING R PLASTIC. ow

,y 1,983,022 AcoUs'rlcAL PLASTER Leslie B. Eaton, Los Angeles, Calif., assignor to Kalite Company, Limited, Pasadena, Calil'., a

corporation of California No Drawing. Application August 19, 1933:, p SerialNo. 685,856

9 Claims. (01. 12-10 This invention relates to improvements in Portland cement or calcined sum laster. acoustical plasters and it particularly relates to The plaster is preferred. a plaster having high sound absorbing properties A preferable mixture consists of 121111; parilzs by for wall coverings, and similar purposes. It is volume of the a re ate to one par y yo ume a continuation in part of my copending appliof the sum faster or two parts of the umice 60 cation Serial No. 578,615, filed December 2, 1931. aggregate to one"p'fit of the gypsum plaster By I have heretofore produced an acoustical plaswe g T 8- bat of DQ 0! 511a! ter having interconnecting pores extending mixture is preferably added an albuminous throughout the thickness of the plaster and f t a ent includin gg al um n and blood i 10 opening into the surface film, which plaster has albumen. Yellow corn dextrine is so prefers. y a higher sound absorbing efficiency than any added 5s a hardener in substantially the relative other mechanically mixed and non-effervescing proportions of three grams of e albumen with plaster heretofore known. I have also discovered six grams of blood albumen an%"28 grams of a that it is possible to apply a coating of acoustical ye ow c r d 'Tfi de i p ves l5 plaster which is also porous and has an improved the Setting D D 0f the p e acoustical effect and higher absorptive coeflicient On a percentage by weight basis, the Preferred 7 of sound absorption, but at the same time is of formula has 1,0110 parts f ggr g te-gl ster sufliciently fine texture to produce a substantially mix e" 0f 2 p 8 g r g 0 D 2 as 8 i smooth outer surface as contrasted with the By weight; to which is a e approximate y normal acoustical products which have an. unts f m dextrme hardener. and m 0-9 6 i, even and pit-ted siuriace. t t d t to 14t.0 12Jarts albumen \{ghich is preferably 1 part I have now pro uced a fine ex ure acous ica egg 0 pa s 51003 a men. plaster which is formed of aggregate which may 'l ft 1albumen p p t lg y be Varied from be ground as fine as minus 20 to plus 100 mesh s i One r m e albumen and two and when mixed with a cementitious binder and grams oibblood albilgen to as much as 15 grams 80 an albuminous agent and water will havea high 0 8 11111611 an 0 Grams of blood albumen. coefiicient of sound absorption. And even though The IQWBI Values are P able because of the the finish coat is trowelled to a smooth hard fin eliitueed rgostd agltd subfitaltially Sat 'Y 7 ish it will not block up but will add to the =a'd- 5 e e rine 61161 is O e that has so vantageous sound absorptive efliciency of the D Yl %1- t1 ry although other ha de e are 85 under coats of acoustical plaster. Such a-proda a a h i uct may also be used as the under or brown coat of Water mixed to P d after being applied either to a hardwall base Plasticity sultajble 9 appllcatlon on all ilor acoustic scratch coat. Under such conditions mgs f the hke wlth Ordmary Plastemlg the wall coating will have increased sound efii- The fimsh coat may be Phomughly troweued to a 0 ciency comparable to other acoustic plasters m hard m? and 15 found on rePeated tests heretofore developed by me. The finish coat to have coefiment of Sound absorptmn of 35% or over at 512 double vibrations for a thickness preferably applied to the undercoat acoustical plasters in thicknesses of approximately oneof-one'half inch ms is when It has been 40 mm inch I I v plled or; a base of ordinary hard wall plaster 5 Other features and advantages of my? new l g fln lowgcofemcient of 9 9: plaster will appear from the following descrlp- This plaster may be applied to any base or tlon thereof which describes a preferred forlrrof dercoat although most eflective acoustic proneb i whlch has Proved to be hlehly efiectlve ties will be found when applied in two coats, the 190 1n browning coat and finish coat each havin an The acoustical plaster in its preferred form has aggregate which is preferably ground t f as its principal in die a fi e ou d a s' mately minus 20 mesh to which ordinary gypsum V gate which may be either mineral or fibrous such or stucco plaster may be'added asa binder. As 215W shredded cane fiber or k r z described with the finish coat, the proportion of ios althogig i fit ilnfigus materlarills slcllfae pumice three or fourf parts of 511111108131 liglht aggregate as n rma o in oca 10 a1 orma eone par 0 gypsum yweig is so pre erred posits i P h aggregate is p ferably for the underccat. It may be desirable in some grou gto minus 20 to plus mesh or finer and cases to apply the plaster over a scratch coat and is mixed with a cementitious binder such as. whereascratch coatisused it may desirably have to curved surfaces and run into molds and as it is made without hair, felt or fiber and preferably has a mineral base it is vermin and germ proof. Furthermore, as the mixture is mechanically made without recourse to chemicals which effervesce there is nothing in the mix that will spoil and extreme rapidity of application is unnecessary. The plaster may therefore be handled in the usual manner of any gypsum plaster.

For convenience in application and in shipment the materials including the aggregate, cementitious binder and albumens are mixed and shipped to the job in a dry form. It is therefore only necessary at the job to add the proper amount of water to secure the desired plasticity. I

It is my belief that the high sound absorbing efiiciency'of my acoustical plaster is due to its surface porosity and to the fact that the inner pores or cavities are 100% intercommunicating from front to back of the plaster so that sound waves entering the surface pores are reverberated through the labyrinth of sub-surface cavities until they are absorbed. The frothing agent materially assists in forming these inner pores and although a finer and more dense aggregate is used for the surface or finish coat, the previously entrapped air bubbles dry and disintegrate, thus forming completely intercommunicating pores throughout the material. I V

While I am aware that modifications may be 'i made to the formula of the product set forth, it

is to be understood that the product is a preferred one and that certain modifications may be made thereto within the scope and spirit of this invention, and I therefore desire a broad interpretation of this invention within the scope and spirit of the description thereof and of the claims appended hereinafter.

:I mr 1' 1. An acoustical plaster for a wall surface which comprises a finely ground mineral aggregate, ground to a fineness of minus 20 to plus 100 mesh, a plaster binder, an albuminous frothing agent, and a dextrine hardener.

. 2. A dry mix plaster product which comprises approximately of pumice aggregate ground to minus 20 to plus 100 mesh, of a calcined gypsum plaster, egg albumen and blood albumen 1n the relative proportion of 2 parts of blood albumen to 1 part of egg albumen, and a dextrine hardening agent, said products being mixed dry and when rendered plastic by the addition of water, forming a plastic coat applicable to a wall surface by, ordinary plastering tools and when trowelled to a smooth surface finish having a sound absorption in excess of.30% at 512 double vibrations in a thickness of inch.

3. An acoustical plaster finish coat applicable by ordinary hawk and trowel methods, comprising an aggregate, a binder, an albuminous frothing agent, a hardening agent and water, the aggregate being ground to a fineness of the order of minus 20 mesh, said coat when trowelled having a smooth surface which on drying will have a hard microscopically porous sound absorptive structure from front to back thereof with intercommunicating pores.

4. An acoustical plaster surface applicable by hawk and trowel methods in a plurality of coats,

.each of said coats comprising a finely ground aggregate, a cementitious binder and water forming a porous structure, and an albuminous frothing agent, the final and browning coats having a relatively more finely ground aggregate than the scratch coat, said final coat when dry having a cellular, porous, sound absorptive structure from front to back thereof with intercommunicating pores, said finish coat having a trowelled, smooth, hard and microscopically porous surface. 5. An acoustical plaster surface applicable by hawk and trowel methods in a plurality of coats, each of said coats comprising an ag regate, a

plaster binder, an al hardening agent and water, and final and browning coats having a relatively more finely ground aggregate than the scratch coat, each ofsaid coats when dry having a cellular, porous, sound absorptive structure from front to back thereof with intercommunicating pores, said finish coat having a trowelled, smooth, hard and microscopicallyporous surface. 2;.1' 6. A dry mix acoustical plaster product which comprises in a 1,000 parts by weight batch of two-thirds ground pumice aggregate to one-third. calcined gypsum plaster by weight, an albuminous frothing agent including from between 0.3 parts of egg albumen and 0.6 parts of blood albumen to 4.5 parts of egg albumen and 9.0 parts of blood albumen, said product when gaged with water and applied as a wall coating having -a porous sound absorptive quality. a 7. A scratch coat of plaster which comprises a ground aggregate of the order of minus 5 mesh, a'cementitious binder, an albuminous frothing agent and a hardening agent, said product when dry having a cellular, porous structure from front to back thereof with a relatively high degree of sound absorption. 8. A browning coat of plaster which comprises. an aggregate ground to the order of minus 20 mesh, a cementitious binder, an albumino'us frothing agent, a hardening agent, and water, said product when dry, having a porous surface from front to back and relatively high degree of soundabsorption. 9. A finish coatof acoustical plaster for a wall surface which comprises a finely ground aggregate, a plaster binder and an albuminous froth-,

tlon of 36% at 512 double vibrations in a thick- 

